I had issues with the front cover oil leak, and yes it is a composite/plastic. However I believe it was a failure of the original RTV applied at the engine plant and not the plastic cracked (there are some small plastic "corners" which will crack as you remove it but those pieces are adhered strongly to the RTV and can't take the levering). Its not a trivial fix, I got lucky and changed it with the aid of superdetailed cleaning and more RTV but to actually change the cover correctly, the oil pan must come off, and I personally consider that an engine removal project to get it right...because there is another joint at the rear of the engine next to the rear crank seal which would also need detailed attention.
That aside I would take a $100 bill and offer that to the current owner to take out for a sea/lake test. It will be the best $100 you ever spent as if there are issues they will become apparent during such a trial and you can research the fixes and enter into negotiations before you actually own it.
In the lake you could also check out things like the trim, listen for u-joint noises with the drive under power, drips into the bilge, other water in the bilge. Check the oil dipstick no matter what it should look like motor oil and not a milkshake (that would seem to indicate a breach between the oil side and the water side of the engine).
Also I highly recommend planning to get on your back and look at the entire hull on a trailer. I looked at one boat which had a 1-1/2" wide strip on the apex of the V on the lower hull rubbed completely off with plywood showing for about 60" long...guessing they rubbed it on a lift more than once...I drove away from that one as fast as possible.